Lymphocyte activation gene-3 (LAG-3; CD223) is a type I transmembrane protein that is expressed on the cell surface of activated CD4+ and CD8+ T cells and subsets of NK and dendritic cells (Triebel F, et al., J. Exp. Med. 1990; 171:1393-1405; Workman C J, et al., J. Immunol. 2009; 182(4):1885-91). LAG-3 is closely related to CD4, which is a co-receptor for T helper cell activation. Both molecules have 4 extracellular Ig-like domains and require binding to their ligand, major histocompatibility complex (MHC) class II, for their functional activity. In contrast to CD4, LAG-3 is only expressed on the cell surface of activated T cells and its cleavage from the cell surface terminates LAG-3 signaling. LAG-3 can also be found as a soluble protein but it does not bind to MHC class II and its function is unknown.
It has been reported that LAG-3 plays an important role in promoting regulatory T cell (Treg) activity and in negatively regulating T cell activation and proliferation (Workman C J, et al., J. Immunol. 2005; 174:688-695). Both natural and induced Treg express increased LAG-3, which is required for their maximal suppressive function (Camisaschi C, et al., J. Immunol. 2010; 184:6545-6551 and Huang C T, et al., Immunity. 2004; 21:503-513). Furthermore, ectopic expression of LAG-3 on CD4+ effector T cells reduced their proliferative capacity and conferred on them regulatory potential against third party T cells (Huang C T, et al., Immunity. 2004; 21:503-513). Recent studies have also shown that high LAG-3 expression on exhausted lymphocytic choriomeningitis virus (LCMV)-specific CD8+ T cells contributes to their unresponsive state and limits CD8+ T cell antitumor responses (Blackburn S D, et al., Nat. Immunol. 2009; 10:29-37 and Grosso J F, et al., J. Clin. Invest. 2007; 117:3383-3392). In fact, LAG-3 maintained tolerance to self and tumor antigens via direct effects on CD8+ T cells in 2 murine models (Grosso J F, et al., J. Clin. Invest. 2007; 117:3383-3392).
Immune tolerance observed in the setting of tumor development and tumor recurrence, however, seems to be mediated by the co-expression of various T cell negative regulatory receptors, not solely from LAG-3. Data from chronic viral infection models (Blackburn S D, et al., Nat. Immunol. 2009; 10:29-37, Grosso J F, et al., J. Clin. Invest. 2007; 117:3383-3392, and Lyford-Pike S, et al., Cancer Res. 2013; 73(6):1733-41), knock-out mice (Woo S R, et al., Cancer Res. 2012; 72:917-927; Okazaki T, et al., J. Exp Med. 2011; 208:395-407, and Bettini M. et al., J. Immunol. 2011; 187:3493-3498), tumor recurrence models (Goding S R, et al., J. Immunol. 2013; 190(9):4899-4909) and, to a more limited extent, human cancer patients (Goding S R, et al., J. Immunol. 2013; 190(9):4899-4909, Matsuzaki J, et al., Proc. Natl. Acad. Sci., USA. 2010; 107:7875-7880, and Gandhi M K, et al., Blood. 2006; 108:2280-2289) support a model wherein T cells that are continuously exposed to antigen become progressively inactivated through a process termed “exhaustion.” Exhausted T cells are characterized by the expression of T cell negative regulatory receptors, predominantly CTLA-4, PD-1, and LAG-3, whose action is to limit the cell's ability to proliferate, produce cytokines, and kill target cells and/or to increase Treg activity. However, the timing and sequence of expression of these molecules in the development and recurrence of tumors have not been fully characterized.
Programmed Cell Death 1 (PD-1) is a cell surface signaling receptor that plays a critical role in the regulation of T cell activation and tolerance (Keir M E, et al., Annu Rev Immunol 2008; 26:677-704). It is a type I transmembrane protein and together with BTLA, CTLA-4, ICOS and CD28, comprise the CD28 family of T cell co-stimulatory receptors. PD-1 is primarily expressed on activated T cells, B cells, and myeloid cells (Dong H, et al., Nat Med. 1999; 5:1365-1369). It is also expressed on natural killer (NK) cells (Terme M, et al., Cancer Res 2011; 71:5393-5399). Binding of PD-1 by its ligands, PD-L1 and PD-L2, results in phosphorylation of the tyrosine residue in the proximal intracellular immune receptor tyrosine inhibitory domain, followed by recruitment of the phosphatase SHP-2, eventually resulting in down-regulation of T cell activation. One important role of PD-1 is to limit the activity of T cells in peripheral tissues at the time of an inflammatory response to infection, thus limiting the development of autoimmunity (Pardoll D M., Nat Rev Cancer 2012; 12:252-264). Evidence of this negative regulatory role comes from the finding that PD-1-deficient mice develop lupus-like autoimmune diseases including arthritis and nephritis, along with cardiomyopathy (Nishimura H, et al., Immunity, 1999; 11:141-151; and Nishimura H, et al., Science, 2001; 291:319-322). In the tumor setting, the consequence is the development of immune resistance within the tumor microenvironment. PD-1 is highly expressed on tumor-infiltrating lymphocytes, and its ligands are up-regulated on the cell surface of many different tumors (Dong H, et al., Nat Med 2002; 8:793-800). Multiple murine cancer models have demonstrated that binding of ligand to PD-1 results in immune evasion. In addition, blockade of this interaction results in anti-tumor activity (Topalian S L, et al. NEJM 2012; 366(26):2443-2454; Hamid O, et al., NEJM 2013; 369:134-144). Moreover, it has been shown that inhibition of the PD-1/PD-L1 interaction mediates potent antitumor activity in preclinical models (U.S. Pat. Nos. 8,008,449 and 7,943,743).
Patients with metastatic or refractory solid tumors have very poor prognosis (Rosenberg S A, et al., Cancer immunotherapy in Cancer: Principles & Practice of Oncology (Eds DeVita V T, Lawrence T S and Rosenberg S A) 2011; 332-344 (Lippincott Williams & Wilkins, Philadelphia Pa.)). Despite advances in multimodal therapy, increases in overall survival in this patient population have been limited. Accordingly, it is an object of the present invention to provide improved methods for treating subjects with such tumors (e.g., advanced refractory solid tumors).